(a) Field of the Invention
The present invention relates to a discharge device which performs streamer discharge and an air purifier. In particular, it relates to a technology for reducing noise of streamer discharge.
(b) Background Information
Air purifiers provided with discharge devices have conventionally been used as a means of decomposing and removing odorous components and hazardous components by using plasma generated by discharge. Among various discharge-based air purifiers, a streamer discharge-based air purifier is suitable for decomposition of the hazardous components and deodorization due to its high decomposition efficiency at a relatively low electric power.
FIG. 8 shows a schematic configuration of a discharge device in an air purifier. The discharge device (29) includes projecting discharge electrodes (30) for generating low temperature plasma and flat counter electrodes (31) opposed to the tips of the discharge electrodes (30). Discharge is caused between the electrodes (30) and (31) to generate the low temperature plasma, and then a target gas is introduced therebetween to allow hazardous components and odorous components contained in the target gas to contact active species (fast electrons, ions, radicals and other excited molecules) generated by the low temperature plasma. In this way, these components are decomposed and removed (for example, see Japanese Unexamined Patent Publication No. 2002-336689).
However, streamer discharge makes a relatively loud discharge sound due to electrical breakdown in the air. Since the frequency range of the discharge sound is significantly likely to be perceived by human hearing, the discharge sound caused by the operation of a streamer discharge-based air purifier may possibly be recognized as a noise. Therefore, the streamer discharge-based air purifier is regarded as unsuitable for places where certain silence is required such as living space and small stores. However, to put it the other way around, if the discharge sound made by streamer discharge can be reduced, streamer discharge will be applicable to compact air purifiers for consumer use. That is, it will be possible to make full use of the high decomposition efficiency of streamer discharge in a wide range of fields.